Glass mat for reinforcing plastics



G. SLAYTER GLASS IIAT FOR REINFORCING PLASTICS ZSHEETS-SHEET 1 .Glam a.Slagter @IVIO EN EY Dec. 4, 1951 File Jan. 11, 1946 G. sLAYTER2,577,214

GLASS um'v FOR REINFORCING PLASTICS 2 slams-Smm 2 Fi-ied Jan. 11, 1946umn l-um r. e@ m w uf m s M HJ m5, m M l a Y m M W Patented Dec. 4, 1951GLAss MAT Fon nEmFoncmG PLASTICS Games Slayter, Newark, Ohio, assignorto Owens- Corning Fiberglas Corporation, a corporation of DelawareAppucation January `11, 194s, semi N6. 640,565

'z claims. (cl. isi-4e) This invention relates to improved reinforcedplastics or plastic laminates. i

An object of this invention is .to provide a plastlc laminate having ahigh concentration of reinforcing glass fibers arranged in strand formto substantially increase the strength of the laminate in any selecteddirection or in practically all directions in the plane of the laminate,depending upon the use to which the laminate is to be put. y y

Another object of this invention is to provide a laminable plasticmaterial having a fibrous glass reinforcement comprising a mass of glassfibers bonded together with the fibers extending predominantly in thedirection or directions along which maximum strength is desired. Thistype of production than other proposed types and not Figure 1 is adiagrammatic side elevation of one type of apparatus for producingfibrous glass reinforcing sheets embodying this invention;

' Figure 2 is a sectional view through the blower end with apparatusshown in Figure 1;

Figure 3 is a diagrammatic plan view illustrating one typicalarrangement of fibers in the mat;

Figure 4 is a diagrammatic plan view illustrating another arrangement offibers;

yFigure 5 is an enlarged diagrammatic sectiona view of a plasticlaminate formed in accordance i with this invention;

reinforcing sheet lends itself to more economical forced laminates to aminimum, but in addition,

enables obtaining a wider variety of strength characteristics. In otherwords, the pattern of the fibers making up the mat may bereadily-controlled so that the fibers extend predominantly in any oneselected direction or in practically al1 directions parallel to thesurface planes of the mat.

A further object of the invention is to provide a fabric-like mat ofglass fibers bonded together at a light density and in which the fibersare in the form of dense bundles of substantially continuous length.

A still further object of the invention is to provide a fibrous unwovensheet as a reinforcement for plastics having a high concentration ofsubstantially continuous fibers therein.

Still another object of this invention is to provide a plastic laminatereinforced with a fibrous glass mat of the above general type having asubstantially continuous length and possessing suf` cient fiexibility toenable the mat to be readily rolled into package form. This arrangementfacilitates and materially reduces the cost'of shipping bonded fibrousglass reinforcing sheets to fabricating plants where they may be. usedin producing reinforced plastics or laminates for any one of a varietyof purposes. Inasmuch'as the resin embodied in the fibrous glass sheetsis cured prior to packaging, the sheets may be packed at greaterdensities than uncured resin impregnated material and need not beshipped in refrigerated space. l

The foregoing as well as other objects will be made more apparent asthis description proceeds, especially when considered in connection withaccompanying drawings, wherein:

Figure 6 is a diagrammatic plan view of the sheet shown in Figure 5;

Figure 7 is a diagrammatic end view of the apparatus shown in Figure 1;

Figure 8 is a side elevation partly in section of another typ'e ofblower; and

Figure 9 is a diagrammatic elevational view of another form of matforming apparatus.

' A plastic laminate Ill embodying a fibrous mat reinforcement isdiagrammatically shown in Figure 5 of the drawings in somewhatexaggerated form. This laminate may be formed of practically any of thecommonly known laminating resins of the low pressure forming and curingor contact pressure types. These `resins cure at temperatures of 225 F.or less and at pressures which may be only contact of one part withanother. 'Ihe present laminate is reinforced with an integral relativelythin mat l l of fibrous glass. As will be presently set forthmore indetail the mat `II can be formed in considerable lengths and possessessufficient flexibility to enable packaging the same in roll form at adensity substantially higher than the normal density of the mat. A1-though other fibrous materials may be used, nevertheless, glass fibersare preferred, because they may be economically produced insubstantially continuous lengths and possess a much higherstrength-weight ratio than other types of fibers. The fibrous glass maybe in the form of strands, slivers, rovings or yarns of glass fibers,which may be produced by any of the processes disclosed in the Slayterand Thomas United States Patent No. 2,133,238 dated October'll, 1938.

Regardless of the particular form of brous glass employed, the fibersare preferably of considerable length as such fibers impart greaterstrength tothe mat. Aswill be more fully hereinafter set forth, the matis built up with either a random or a more or less uniform arrangementof fibers. depending upon the use to which the mat is to be put.However, the pattern of the fibers is preferably controlled so that thefibers extend predominantly in the direction or directions along whichmaximum strength is desired, and this feature is of prime importancewhen usingl the mat as a reinforcement for thin plastic laminates. Ininstances where maximum strength is desired in all directions parallelto the mat, the fibers are laid in layers with the fibers in adjacentlayers oriented to extend predominantly in different directions. l

It has been stated above that the characteristics of the bonded fibrousglass mat is such as to enable rolling the mat into a package of higherdensity than exists in the actual mat. This feature greatly facilitatesand reduces the cost of shipping as it enables a greater quantity ofmaterial to be accommodated in less shipping space. In addition, thenecessity of using refrigerated carriers on account of the resin isavoided because the resin binder may be cured. partially cured or driedprior to packaging the mat. Furthermore, by curing or drying the resinbinder prior to packaging the mat, suiflcient integrity and strength isimparted to the mat to enable shipping the same in a relatively lightweight carton of inexpensive paper or the like.

Mats formed in the manner of the present invention are adaptable toproducing a wide variety of products. The mat is normally formed at alight density of from l/2 to 21/2 pounds per cubic foot and in this formmay be laminated to produce light density products such as thermalinsulation or compressed to higher densities for molded articles.

I It follows from the above that the material itself may not only beinexpensively produced on a production basis, but may be economicallyshipped to remote plants as a prefabricated sheet capable of beingtailored to size for use as a reinforcement for plastics, pipecoverings, acoustical light shades, linoleum base and such other usesrequiring a thin, light weight, extremely strong reinforcement. Anotherfeature of the bonded sheets is that the thin mat has sufficientintegrity to withstand the stresses of dipping or pulling through abatch of laminating resin.

The method of forming the ,product previously described will be morefully understood upon considering one type of apparatus suitable forcarrying out the several steps of the method. The apparatus isschematically shown in several figures of the drawings and, referringparticularly to Figure 1, it will be noted that the reference characterI2 indicates an endless belt-type conveyor adapted to be driven by anysuitable mechanism in the direction of the arrow A. The glass fibers instrand form are designated by the reference character I3 and aredistributed on the conveyor I2 from a position spaced above the latter.In the present instance, the fibrous glass lstrands I3 are respectivelypackaged on spools I4 supported on any suitable `frame structure (notshown) in spaced relation to each other transversely of the conveyor I2.The strands themselves may be either groups of one hundred or moreindividual fibers having little or no twist or they may be twistedand/or plied yarns in which form greater strength and integrity in thestrand is realized.

The fibrous glass strands are removed from the spools I4 and aredeposited on the conveyor I2 by circular type blowers I5 correspondingin number to the number of strands I3 and are supported in any suitablemanner between the spools I4 and the top of the conveyor I2. Uponreference to Figure 2 of the drawings, it will be noted that the blowersI5 are each formed of separable sections I6 and I'I. These setion of themat from the con cooperate with one another to form an air chamber I8and to provide a conical chamber I9 at the center of the chamber I8. Theconical chamber I9 is directed toward the discharge side of the blowerand communicates with the chamber I8. The section I6 of the blower isformed with a central aperture 20 aligned with an inlet aperture 2Iformed in the blower section I1. The fibrous glass strands I3 arerespectively threaded through the inlet apertures 2| and dischargeapertures 20 of the blowers I5 in the manner shown in Figure 2 of thedrawings. Air under pressure from a suitable source of supply isintroduced through a conduit 22 into the chamber I8 and is dischargedthrough the outlet aperture 20. As the air under pressure flows out ofthe blower through the discharge passage 20, it envelopes the strand I3and pulls the strand through the blower. The air pressure is, of course,sufficient to unwind the strands from the packages I4 and to project thestrands downwardly onto the top of the conveyor I2. A driven feed rollI4a about which the strand is passed may be employed to provide auniform control of the strands I3 as they are projected bythe blowersonto the belt. In this way an individual blower is prevented fromdrawing greater amounts of strand through adjacent blowers and thusproducing an uneven thickness in the mat.

The fibrous glass is deposited on the conveyor I2 in a haphazard mannerto provide a mat of iibrous glass wherein the fibers cross and overlapeach other. The diversity of the fibrous glass may be controlled by therelative speed of movement of the conveyor I2 and the rate at which thestrands are blown through the blowers onto the conveyor.

As the mat of fibrous glass is formed on the conveyor I2, it issaturated with a suitable thermosetting resin from spray heads 22@L andis conveyed through a heating zone 23 by a second endless belt-typeconveyor 24. The belt-type conveyor 24 is spaced in the direction oftravel eyor I2 in order to enable excess resin to drain from the matbefore it is introduced to the conveyor 24. If desired, heat may beapplied to the underside of the mat as it is conveyed through the spacebetween the conveyors, so as to partially cure the resin and therebyprevent the mat from adhering to the conveyor 24 while it is beingadvanced through 'the heating zone 23. The heat at the zone 23 issupplied 4by a suitable oven 25 and is sufficient to polymerize thethermosetting resin to a final set in a relatively short space of time.

Various thermosetting condensation products may be used as a binder,such for example, as phenol formaldehyde, urea formaldehyde, or variousmodiiications and variations of these synthetic materials. However, forordinary uses of the mat, it `has been found that phenol formaldehyderesin is highly satisfactory when applied in solutions containing 5 to10% solids. In general practice the finished product may comprise about22 to 30% glass fibers and 70 to 78% resin although these amounts mayvary according to the manner in which the mats are to be used. As littleas 2% of resin may at times be suflicient to provide adequate handlingcharacteristics.

Regardless of the specific thermosetting resin used in forming the mat,the latter is provided with a concentration of glass fibers which extendin a number of different directions generally parallel to the plane ofthe top and bottom surfaces of the mat. This is due to the fact that thebrous glass strands-are deposited at random on the conveyor I2 by theblowers I5 and this haphazard orientation `of the glass fibers impartsstrength to the mat in a multiplicity of directions. In actual practice,the lthickness of the fibrous mat and the quantity ofI resin employed isdetermined to provide a mat having suiiicient flexibility to'enablerolling the mat leaving the delivery side of the conveyor 24 yinto apackage 26 having a density substantially greater than the normaldensity of the mat. Thus, prefabricated bonded glass liber mats ofpractically any desired lengthmay be packaged into a relatively smallspace and shipped to the tabricator for incorporation in the desiredproduct. f

The preferred use for a mat embodying the present invention is toreinforce thin plastic laminates which require substantial strength inone or more specified directions parallel to `the plane of the laminate.Accordingly, it is important to control the disposition of the iibrousglass on the conveyor I2 and thereby insure obtaining the berorientation required to give the maximum strength in the specifieddirections. One 'arrangement of the fibers which provides a mataffording substantial strength in practically all directions parallel tothe mat is shown 'in Figure 4 of the drawings. In this gure,`thereference character 21 indicates in broken lines a plurality ofstationary, circular type blowers similar to'the blowers I5 andsupported above the conveyor I2 in spaced relation to each othertransversely of the conveyor. This bank of blowers serves to lay down onthe travelling belt-type conveyor a plurality of fibrous glass strandsin a pattern which may at times approximate an extended spiral formextending predominantly in the direction of conveyor travel indicated bythe reference character A. A second bank of blowers 23 is suspendedabove the conveyor I2 in spaced relation to each other in the directionof travel of the conveyor. This bank of blowers is supported by amovable framework (not shown) for movement transversely of the conveyorback and forth in the direction indicated by the arrow B,in Figure 4 ofthe drawings. Thus, the bank of blowers 28 lays down fibrous glassstrands which extendl predominantly crosswise of the strands laid downby the blowers 21 and produce three distinct layers due to the movementof the conveyor. The arrangement is such that the fibrous glass strandsin adjacent layers of the mat extend in different directions and impartsubstantial strength to the mats in corresponding directions.

Another arrangement that may be employed to provide a thin mat havingsubstantial strength in practically all directions parallel to the matis shown in Figure 3 of the drawings. In this figure of the drawings,the reference character 29 indicates a bank of blowers similar to theblowers I5 and supported above the conveyor I2 in spaced relationtransversely of the conveyor. The bank of blowers 29 serve to lay thefibrous glass strands down on the conveyor in overlapping circularpatterns indicated by the reference character 30 in Figure yf3 of thedrawings. For accomplishing this result, the blowers 29 are equippedwith -a guide 3|, which extends downwardly from the discharge aperture20 of the blower and is supported on the blower for universal movement.The arrangement is such that air under pressure flowing through thedischarge opening 20 in the blower imparts a gyrating motion to theguide 3| and the latter, in turn, reacts on the fibrous ing around apulley 33 secured to the guide. As

a result, the fibrous glass strand is deposited on the conveyor I2 inthe form of loops and the arrangement of the blowers is such that theloops of one strand overlap the loops of an adjacent strand. These loopsare, of course, formally united together by polymerization of thethermosetting resin applied to the strands as they are built up to formthe mat II.

A still further method of producing fibrous glass mats of the generaltype illustrated in Figure 3 comprises the apparatus showndiagrammatically in Figure 9. As illustrated in the drawing a pluralityof spools or packages of strands 35 are mounted in banks to forma creel36 and are arranged so that the strands can be drawn through a series ofguide eyes 31. In'this way any desired number of single strands can begathered together from each tier of spools. 'I'he strands drawn from theendof the spools have a natural low degree twist and readily intertwinewith each other to form a single integral strand 38.

This strand 38 passes between constantly rotating feed rolls 39 and isallowed to fall at random on a moving conveyor belt 40. Due to theinherent combined twist in the strand `the strand tends to form in coilson the conveyor surfacewith a waving or undulating motion. The tendencyto coil is controlled somewhat Iby the distance of the feeding rollsfrom the conveyor and the motion is augmented by the blast from a sprayhead 4I by means of which binder is applied.

The creel 36 is arranged so that a plurality of strands 38 aresubstantially uniformly spaced across the conveyor width. This spacingis such that the coils formed from adiacent strands overlap each otherat times and interlock so that when held together bythe binder a singlesheet of mat comprising fibrous glass and having substantiallycontinuous glass fibers in the form of integral twisted strands arrangedin overlapping distinctly formed loop formation extending substantiallyuniformly over the width and length of the mat whereby said loopsintermingle with adjacent loops, anda bonding material securing saidloops together.

2. A glass fiber mat comprising a sheet of fibers folded upon itself toform layers of. glass fiber mat in which the fibers in each layer are inthe form of continuous strands arranged substantially in rows ofoverlapping coils, the coils in each row overlappingA adiacent rows, andthe rows in each layer extending at an angle to the rows of adjacentlayers.

3. A glass fiber mat comprising a sheet of fibers folded upon itself toform layers of glass fiber mat in which the fibers in each layer are inthe form of continuous strands arranged in rows of overlapping coils,the coils in each row overlapping adjacent rows, and the rows in eachlayer extending at an angle to the rows of adjacent layers, said rows ofcoils extending lconglass strand to impart a helical contour to thetinuously through at least two of said layers.

distinct closed coils, the coils of each strand over-- lapping adjacentcoils of that strand and overlapping the coils of adjacent strands, anda bondingmaterial securing said coils together.

5. As a product of manufacture, a mat for the reinforcement of plasticscomprising substantially continuous glass fibers in which the bers arein the form of strands having a natural low twist, said strands arrangedin rows of a multiplicity of overlapping loops formed by the undulatingfall of said strands by gravity, said mat being folded upon itself toform layers, and a bonding material securing the strands and layerstogether.

6. As a product manufacture, a sheet for the reinforcement of plasticscomprising a mat of substantially continuous glass fibers in which thefibers are in the form of a juxtaposed series of intertwined twistedstrands, said strands forming substantially parallel rows of amultiplicity of substantially closed overlapping coils resulting fromthe normal tendency of the strands to form coils as they fall bygravity, and a synthetic resin bonding said coils together.

7. As a product of manufacture, a sheet for the reinforcement ofplastics comprisingamatformed of a plurality of Vtwisted strands ofcontinuous, length each disposed spirally in a series of closed loops,the loops of one ystrand overlapping the loops of vadjacent strands toprovide a substantially continuous body of strands.A in which thestrands extend in all directions,` substantially ln4 the plane of themat, and a bonding materialsecuring said loops together. v

GAlVIES SLAYTER.

REFERENCES errno UNITED STATES PATENTS Number Name Date 1,315,409Ramsbottom Sept. 9, 1919 1,365,061 Respress Jan. 11, 1921 1,478,862Rosenthal Dec. 25, 1923 2,015,006 Ekisler Sept. 17, 1935 2,117,371Slayter May 17,r 1938 2,392,882 Roberts Jan. 15, 1946 2,429,688 HooverOct. 28, 1947 FOREIGN PATENTS Number Country Date 17,549 Great Britain1898

1. A STRONG RESILIENT, LIGHT WEIGHT POROUS SHEET COMPRISING FIBROUSGLASS AND HAVING SUBSTANTIALLY CONTINUOUS GLASS FIBERS IN THE FORM OFINTEGRAL TWISTED STRANDS ARRANGED IN OVERLAPPING DISTINCTLY FORMED LOOPFORMATION EXTENDING SUBSTANTIALLY UNIFORMALY OVER THE WIDTH AND LENGTHOF THE MAT WHEREBY SAID LOOPS INTERMEDIATE WITH ADJACENT LOOPS, AND ABONDING MATERIAL SECURING SAID LOOPS TOGETHER.